Self-expanding stents are valuable prostheses for keeping lumen open and preventing closure due to a stricture, external compression, or internal obstruction. In particular, stents are commonly used to keep blood vessels open in the coronary arteries and they are frequently inserted into the ureters to maintain drainage from the kidneys, the bile duct for pancreatic cancer or cholangiocarcinoma or the esophagus for strictures or cancer. Additionally, stents may be formed specifically for alternative indications such as sealing a bleb, serving as a vehicle for drug administration or air removal from a bleb, etc.
Though stents are excellent devices when used properly, improper installation can lead to tissue luminal inflammation and tissue granulation. In particular, many physicians introduce stents with catheters and other delivery devices that do not give them adequate visual certainty that the device has been installed at the desired target site. Moreover, devices that allow for limited visual feedback have an excessively large diameter, which can hinder patient ventilation. Additionally, such devices do not have safety features to ensure that the stent is not prematurely and irretrievably deployed.
In order to facilitate the delivery of stents, medical device companies began to design deployment apparatuses that allow physicians to deploy stents more precisely. Unfortunately, guidance of the stent has substantially remained a function of physician skill resulting from substantial practice. This fact has become particularly evident with the advent of radially expanding stents. If after full deployment of the stent, the physician discovers the stent has been implanted incorrectly, there is no conventional way of correcting the error short of removing the stent. In particular, as a rule of thumb, once the exterior catheter, of conventional delivery devices, has been retracted beyond 60%, it generally cannot be realigned with respect to the stent. As a result, physicians must be sure of their stent placement prior to deploying the stent beyond the 60% point. We will refer to this 60% point throughout the application as the critical deployment point.
Conventional stent delivery devices, however, do not have any safety mechanism to prevent excessive deployment of a misaligned stent. In fact, conventional delivery devices require the physician to estimate extent of deployment, which results in either overly conservative or excessive deployment—both of which leads to stent misplacement.
Misplacement is often a function of a physician's inability to directly visualize the target area and the route thereto. Attempts have been made to provide scopes as postscript additions to existing devices, with little or no thought about the functionality of such arrangements. As a result visualization features are not directly integrated into the design of these devices and therefore substantially limit their efficacy.
An additional limitation of conventional stent delivery devices is the distal tip of conventional stent delivery devices are not adequately designed to (1) facilitate the clearance of obstructed lumen, or (2) facilitate the removal of the delivery device once the stent is radially expanded. In particular, most distal tips are not configured to comfortably guide the delivery device through a diseased or occluded lumen so that the stent can be delivered in the most beneficial location. Moreover, once the stent is radially expanded conventional designs rely exclusively on dimensional mismatching to ensure proper removal of the delivery device. In the event the stent does not adequately expand to preset dimensions, a conventional delivery device would be stuck in the patient until some invasive procedure is performed to remove it and the defective stent.
Therefore, there remains an existing need for a stent deployment apparatuses that has a safety mechanism to prevent excessive deployment of a misaligned stent. Preferably it would be desirable if the safety mechanism had a physical and/or audible indication means to inform the physician when she has reached maximum reversible deployment. As an additional safety feature, there is an existing need for a distal tip designed to allow for the removal of the deployment apparatus even if the stent does not radially expand to its preset expansion diameter. An existing need also exists for a stent deployment apparatus that has a distal tip adequately configured to navigate through diseased and/or occluded lumens so that the stent can be delivered to this target area.
There also remains an existing need for a stent deployment apparatus that increases physician control during stent deployment. Moreover, there exists a need for a stent deployment apparatus that allows for the insertion of an optical scope to facilitate stent delivery. In particular, there is an existing need for a delivery device that allows for the direct visualization of lumens via a variety of optical configurations. For example, optical scopes can be directly integrated into the inner dimensions of the device or receivable about the inner or outer dimensions of the inner and outer tubular members. Additionally, there is a need for a device that provides visualization windows to enhance the physician's field of view during deployment.